The present invention relates to photovoltaic modules set on, for example, a roof of a building, and more particularly, to photovoltaic modules with an improved output fetching wiring unit and a power generation system using the same.
The output of a crystalline or amorphous photovoltaic module is conducted to the outside through terminals that are set on the back surface of the module. In general, there are two types of terminals, ones for positive and negative electrodes. In some cases, these terminals are housed in a terminal box as it is called. A terminal box of one known type can contain therein both the terminals for positive and negative electrodes, while another type is designed to contain each of these terminals. A conduction path which is connected to each terminals for the module output is described in Jpn. Pat. Appln. KOKAI Publication No. 10-256578. This conduction path is an output fetching wiring unit that includes a pair of busbars, positive and negative, attached individually to the opposite ends of the photovoltaic module. In the conventional wiring unit described in the KOKAI Publication (""578), metallic foils on the back surface of the photovoltaic module and the busbars are connected electrically to one another by means of an electrically conductive material such as electrically conductive paste. Lead wires that serve as output fetching lines are soldered to the metallic foils, individually. These lead wires are drawn out of the module through a protective film (cover film) on the back surface of the photovoltaic module. The lead wires are connected individually to terminals of a terminal box or the like that is provided on the back surface of the photovoltaic module, if necessary.
In an output fetching wiring unit described in Jpn. Pat. Appln. KOKAI Publication No. 9-326497, as shown in FIGS. 23A to 23C, one end portion of each lead wire as an output fetching line is soldered to each of the positive and negative busbars 200 and 201 that are attached individually to the opposite ends of a photovoltaic module. The respective other end portions of the lead wires 202 are drawn out through a protective film (cover film) 203 on the back surface of the photovoltaic module and soldered individually to terminals of the terminal box.
Conventionally, if the wiring direction of the output fetching wiring unit is expected to be changed, first and second electrically conductive members that are independent of each other are arranged in a manner such that their respective end portions continuously extend at a given angle to each other, and their overlaps are soldered.
In the conventional output fetching wiring unit constructed in this manner, there is a lot of soldering spots that connect the busbars of the photovoltaic module and the terminal box, and there are also soldering spots in a region where the wiring direction changes. Soldering, which is poor in working efficiency, may cause electrical connection failure. In consequence, the connection is not very reliable, the yield is poor, and the manufacturing cost is high.
Accordingly, the object of the present invention is to provide photovoltaic modules and a power generation system, improved in quality and yield and lowered in manufacturing cost.
In order to achieve the above object, according to the present invention, there is provided a photovoltaic module with a plurality of photovoltaic cells, which comprises a busbar body connected electrically to the photovoltaic cells and an extension extending integrally from the busbar body and serving as an output fetching line. According to the invention, the busbar that is connected to the photovoltaic cells doubles as an output fetching line, so that any other output fetching lines to be prepared independently of the busbar need not be soldered to the busbar. Thus, the number of soldering spots in an output fetching wiring unit can be reduced.
More specifically, the photovoltaic module according to the invention comprises a transparent substrate, the photovoltaic cells arranged on the back surface of the transparent substrate, an electrical insulating filler covering the respective back surfaces of the photovoltaic cells, a cover film covering the filler, and the busbar including the busbar body connected electrically to the photovoltaic cells and embedded in the filler and the extension long enough to project from one end of the transparent substrate, the extension being drawn out through the cover film. The filler functions as an adhesive for bonding the back surfaces of the photovoltaic cells and the cover film.
According to the invention, the busbar itself doubles as an output fetching line, so that it is unnecessary to prepare any other output fetching lines independent of the busbar or to solder the output fetching lines. Thus, the necessary number of soldering spots for the output fetching wiring unit can be reduced. Since the extension of the busbar, which serves as the output fetching line, is turned up on the back surface of the photovoltaic module, it can be confined within the outer peripheral contour of the transparent substrate. Besides, these busbar extensions can be easily connected to terminals that are arranged on the back surface of the module.
A spacer of an electrical insulating material may be used according to the invention. The spacer is put on an end portion of the busbar body. The busbar extension is bent along the spacer and drawn out of the cover film through a through hole in the cover film. An electrical insulating sheet, such as a nonwoven fabric of fiberglass or an insulating resin (e.g. polyvinyl fluoride), may be used for the spacer. In order to improve the electrical insulating properties further, an electrical insulating synthetic resin, such as polyvinyl fluoride, may be used for the cover film. Since longitudinally intermediate portions of the busbar extension are buried in the filler according to the invention, a long sealing distance can be secured for the output fetching line (busbar extension), so that the water resistance is improved. In the case of the electrical insulating spacer is interposed between the busbar extension and the photovoltaic cells, moreover, an electrical short circuit between the output fetching line and the cells can be prevented securely.
According to the invention, the busbar extension may be formed having a bent portion turned down to change the course in the middle in its longitudinal direction so that the wiring direction of the output fetching line can be changed at the bent portion. With this arrangement, it is unnecessary to prepare any electrically conductive member in the region where the direction of the output fetching line changes or to solder the conductive member.
A power generation system according to the invention comprises the photovoltaic module as a generating element in a roofing material or the like. The generating element may be incorporated in a tile body that constitutes a roofing tile.
According to the photovoltaic module and the power generation system of the invention, the number of soldering spots in the output fetching wiring unit is reduced, so that the incidence of failure attributable to soldering is lowered. Thus, the quality and yield of the photovoltaic module, as well as the workability of the wiring unit, are improved, so that the manufacturing cost can be lowered.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.